1. Technical Field
The present invention relates generally to a flywheel assembly, and more particularly, to a flywheel assembly having a flexible plate for elastically connecting an engine crankshaft with a flywheel.
2. Description of the Background
(1) A bending force is exerted on the crankshaft when an engine converts a combustion force Into torque. A flywheel mounted on an end of the crankshaft is thus subjected to bending vibration by the bending of the crankshaft. Subsequently, this vibration force is further transmitted to the engine block, which vibrates the whole body of the vehicle through the engine mount. Consequently, noise is produced at the time of acceleration.
In order to reduce such noise at the time of acceleration, vibration of the flywheel must be reduced. Therefore, the flywheel in conventional devices have been supported by a flexible plate. The flexible plate is high in rigidity in the direction of rotation, while being low in rigidity in the direction of bending vibration.
The flexible plate Is more effective in reducing bending vibration the lower its rigidity. A shifting of the peak resonance point away from the actual use range by employing this kind of low-rigidity flexible plate makes it possible to reduce noise at the time of engine acceleration. However, by lowering rigidity in the direction of the bending vibration the thickness of the flexible plate can be made too small. The respectively higher stress on the flexible plate can act to shorten its life. Subsequently, degradation of clutch disengagement characteristics may occur due to rigidity in the direction of the bending vibration being too low, thereby causing axial movement of the flywheel during the clutch release operation.
(2) A flywheel is mounted on the end of an engine crankshaft of, for example, an automobile. In some cases the flywheel is directly mounted on the end of the crankshaft and in other cases the flywheel is mounted on the end of the crankshaft through a flexible plate. When the flywheel is mounted on the end of the crankshaft through a flexible plate, radially inner portion of the flexible plate is fixed to the end of the crankshaft and radially outer portion of the flexible plate is fixed to the flywheel.
Furthermore, a friction surface is formed on a side surface of the flywheel for pressure contact with friction facings of a clutch disk of a clutch device which is mounted on the radially outer portion of the flywheel.
Friction between the friction surface and the friction facings generates heat in the apparatus. This frictional heat causes, for example, abnormal wear of the friction facings and early degradation of their performance characteristics. In the case of a flywheel mounted on the end of the crankshaft through the flexible plate, the cavity between the flywheel and the flexible plate is particularly liable to be filled with heat.